When an output buffer or the like in the semiconductor device drives. an external high load, the noise is generated on power supply wiring or the like in the semiconductor device. This noise is propagated to respective blocks in the semiconductor device, and causes jitter in a block. Traditionally, this jitter is sufficiently small with respect to an operating frequency of a product. Thus, the influence of the jitter on an operation of the product has never become a problem.
However, in recent years, the number of product configurations each having a plurality of modules mounted thereon for which a high-speed operation is required has increased, so that the jitter caused by the noise often causes a malfunction of the product. For this reason, unless the noise generated inside is measured with a high degree of accuracy and identification of a location that causes the noise (e.g. which portion of the power supply wiring) is performed, analysis at the time of the malfunction of the semiconductor product would become difficult.
Generally, when measuring ringing noise or jitter noise inside the semiconductor device, the measurement was performed by opening a package of a semiconductor product, removing a protective film on the surface of the product and applying needle probes, and performing waveform observation using an oscilloscope. As other method of opening the package and performing the waveform measurement, non-contact waveform observation by using an EOS (electro-optic-sampling) probe is known. When the waveform of the noise is measured by the oscilloscope, internal wiring of the semiconductor product needs to be exposed. Generally, the semiconductor product is enclosed with ceramic or a resin. Then, this enclosure is opened to enable a semiconductor chip to be visually seen. Since the ceramic package is formed of a metallic or ceramic sealing, the semiconductor chip becomes visible when this sealing is removed. In the case of a resin mold, a chemical that dissolves the resin is used to make an opening in the resin mold to a position through which the semiconductor chip can be seen. When the semiconductor chip becomes visible, the protective film that covers the wiring to be measured is removed. Then, an ion beam is irradiated using an FIB (focused ion beam system for focused ion beam processing and observation) or the like to remove the protective film on the molecular basis. When metal wiring of a portion to be measured is exposed, a needle with a leading end thereof being minute, referred to as “probe”, is applied to the metal wiring, and the oscilloscope is connected to the probe. Then, a power supply is connected to the semiconductor product, and the waveform observation is performed while operating the semiconductor product.
When the noise is measured by an EOS probe, the same method as that in the foregoing description is used for processes up to the process of exposing the metal wiring of a portion to be measured. Then, the EOS probe connected to a dedicated measuring system is approached, the power supply is connected to the semiconductor product, and the waveform observation is performed by the dedicated measuring system while operating the semiconductor product. The EOS probe is the probe that utilizes an electro-optical (EO) effect. The electro-optical effect is a phenomenon in which the refractive index of a material varies with an applied electrical field. Since the electro-optical effect extends from a direct-current region to a micro-wave region, the electro-optical effect is applied to various devices such as an optical modulator and an optical switch. These devices are based on a principle in which a change in the phase of light due to the applied electrical field is converted to a change in the intensity of the light by interference, or this change in the phase changes a propagating direction of the light.
On the other hand, a waveform state detection device is disclosed in Patent Document 1 as a related art. In this device, when an abnormality occurs in a waveform, display of the abnormality is performed. According to this device, by using this device for an input signal for performing an edge operation at an input terminal or the like such as a strobe signal or a clock signal other than a bus signal or a state signal, an abnormal state of the signal due to signal reflection can be readily known.
[Patent Document 1]
Japanese Patent Kokai Publication No. JP-P2000-131366A (FIG. 1)